Study on the tightness of detachable and welded joints for helium-cooled devices

Main results of experimental study on helium-tightness of different units and joints are presented. The experiments were carried out to substantiate design solutions to assure circuit tightness during operation of helium-cooled devices. The tests of flange connections showed that the reguired tightness was provided by both serrate gaskets at a flat mirror of a flange and by flat gaskets of annealed copper with corrugated surfaces of a gate at a flange joint of ''tongue-slot'' type. It is shown that in flange joint models, designed for the maximum pressure, P=10 MPa, to provide for the required tightness in helium, the necessary force compressing the gasket exceeds the rated one three times and is 1.5 x 106 N. As a result of tests on tightness of welded joints of austenitic and pearlitic steels, it is established that at a helium pressure of 4.5 MPa and temperature of 350 deg C, with thermocyclic loads being periodically applied, the base metal and welded joints correspond to the 1st-2nd classes of tightness. The results obtained confirm the possibility of creating the helium-cooled circuit possessing a sufficient degree of tightness